In pulp processing devices such as for example presses, cellulose pulp is fed to a pulp web which extends around the press, whereby the cellulose pulp is gradually dewatered along the entire pulp web and preferably the pulp is pressed at the end of the pulp web for further dewatering to desired consistency. Subsequently, it is transported to the next step.
Usually the pulp is pressurised along the entire pulp web and introduced to the pulp web at a certain increased pressure. Two main reasons that the pulp conventionally has been introduced to the pulp web at an increased pressure, i.e. higher than atmospheric pressure, is firstly that thereby a uniform distribution along the entire width of the pulp web is achieved, since the high pressure facilitates forcing the pulp onto the entire width of the web. A second reason is that with the high pressure a more efficient dewatering of the cellulose pulp is accomplished already in the initial part of the pulp web. The high initial pressure has thereby resulted in an improved dewatering of the pulp.
There are, however, problems related to the high pressure. One problem is that the high pressure results in a limitation of the amount of pulp that may be dewatered along a pulp web per time unit. In fact, it has been shown that the pressure builds up along the entire pulp web to continuously increase towards and being topmost at the end of the pulp web, i.e. the nip. Another problem is that it costs energy to pressurise the cellulose pulp to the desired pressure. Moreover a pump and accompanying pipes are needed to build up the pressure and to transport the pressurised pulp to the inlet box. Up to now, no device exists by which one can reliably and without substantial pressure drop distribute pulp to a processing surface to form a pulp web on the same.
In the Swedish patent document 516 335 a device is described for feeding of cellulose pulp in the form of a pulp web. At this device the outlet includes restrictions in the form of holes which are arranged along the generator of the envelope surface of the inlet box. The holes are preferably arranged so that their diameter is smaller than the distance between them. In that way, the pressure is maintained in the inlet box such that the pulp is forced out of the outlet and is uniformly distributed along the width of the pulp web. The said device thus requires a fairly high input pressure to the inlet box, since the pressure drop over the restrictions will be significant.
An object of the invention is to obtain an improved device for distribution of cellulose pulp to a pulp web at a pulp processing device, which device does not show the problems which are present in conventional devices and which are described above.
The said object is achieved by the device as disclosed in the claims, which device is intended for distribution of cellulose pulp with a concentration of 2-13% to a movable processing surface in a pulp processing device to form a pulp web on the said surface, which pulp web is transported with the movable processing surface in a first direction D1, whereby the distribution device comprises:                an inlet box comprising an inlet for incoming cellulose pulp to the inlet box and an outlet for transferring of the cellulose pulp to the pulp web, which outlet opens towards the pulp web and has a length L that corresponds to the width of the pulp web, and which outlet has a width which is delimited by a first long wall and a second long wall which is opposite to and essentially parallel to the first long wall,        a rotating distribution means which is arranged to distribute the cellulose pulp along substantially the entire length of the outlet, and which is arranged between the long walls of the outlet,        
The distribution means is so placed that a first distance a1 between the distribution means and the first outlet wall is larger than a second distance a2 between the distribution means and the movable processing surface.
The invention also relates to a method for distribution of cellulose pulp having a concentration of 2-13% to a pulp web on a movable processing surface in a pulp processing device, which processing surface is moved in a first direction D1, whereby the method comprises the steps of:                feeding cellulose pulp to an inlet box having an outlet which opens towards the pulp web and has a length L which corresponds to substantially the entire width of the movable processing surface, whereby the outlet has a width which is delimited by a first long wall and a second opposed and in relation to the first wall essentially parallel long wall;        by a distribution means in the inlet box distributing the cellulose pulp along substantially the entire width of the pulp web;        
Further, the cellulose pulp is let through the outlet to the pulp web essentially unimpededly, thanks to the distribution means being placed such that a distance a1 between the distribution means and the first outlet wall is larger than a second distance a2 between the distribution means and the movable processing surface.
Thanks to the above described device and method there is no need to feed the cellulose pulp at an increased pressure to the inlet box, whereby the device requires fewer parts, since no pump with accompanying pipes are needed, and since it may be operated at a lower energy consumption. Thus, it becomes cheaper to implement as well as to operate. In addition to a simplification of the feeding to the inlet box the operation of the inlet box becomes safer and the risk of pulp build-up becomes minimal.
The invention also relates to a pulp processing device, comprising the above described device for distribution of cellulose pulp. The pulp processing device may for example have a movable processing surface formed by a rotating roll or a movable processing surface formed by a plane wire.